Omron CJ - INSTRUCTIONS REFERENCE MANUAL 07-2009 Reference Manual page 767

3. Instructions
• High-frequency Calculation Method
In this case, the counting method is switched at high and low frequencies. (Supported by CJM1 CPU
Unit Ver. 3.0 or later only)
• High-frequency counting (C1 = 0 10, 0 20, or 0 30)
At high frequencies (above 1 kHz), the function counts the number of pulses within a fixed interval
(the sampling time) and calculates the frequency from that count. One of the following three sampling
times can be selected by the third digit of C1.
Sampling time
10 ms
100 ms
1 s
Note At frequencies below 1 kHz, the Standard Calculation Method is used, regardless of the sampling time setting.
Converting Counter PV to Total Number of Revolutions (C1 = 0001 hex)
If C1 is 0001 hex, PRV2(883) calculates the cumulative number of revolutions from the counter PV and
pulses/revolution setting.
Conversion result = Counter PV
Precautions
If the counter is reset when C1 specifies frequency-rotational speed conversion for a high frequency,
the data read during the sampling time when the counter was reset will not be dependable.
Sample program
When CIO 1.00 is ON in the following
programming example, PRV2(883) reads the
present pulse frequency at high-speed
counter 0, converts that value to rotation
speed (r/min), and outputs the hexadecimal
result to D201 and D200.
When CIO 1.00 is ON in the following
programming example, PRV2(883) reads the
counter PV, converts that value to number of
revolutions, and outputs the hexadecimal
result to D301 and D300.
730
Value of C1
0 10 hex Counts the number of pulses every 10 ms. The error is 10% max. at 1 kHz.
0 20 hex Counts the number of pulses every 100 ms. The error is 1% max. at 1 kHz.
0 30 hex Counts the number of pulses every 1 s. The error is 0.1% max. at 1 kHz.
Pulses/revolution
Description
1.00
PRV2
#0000
#0003
D200
1.00
PRV2
#0001
#0003
D300
CS/CJ/NSJ Series Instructions Reference Manual (W474)
Converting frequency
to rotation speed
Pulses per revolution
Converting counter PV to
total number of revolutions
Pulses per revolution